Multi Gigabit/s optical transmissions systems have been proposed which multiplies the capacity (bit/s) transported over an optical fiber (within a given spectrum) by moving to a multimode fiber (MMF) and by transporting different data channels over the different spatial modes (and possibly the different polarization modes) of the MMF. In other words, mode division multiplexing (MDM) over multimode fiber (MMF) is investigated as one of the options to overcoming the capacity limits of standard single-mode fibers (SMF).